The present invention relates to a tire tool and more particularly to a tire caliper for comparing the diameters of a plurality of tires that should be matched for use.
Motor vehicle tires, supposedly of the same size, often vary considerably in diameter when new. Also tires on a vehicle frequently wear at unequal rates. The resulting differences in diameters between tires that are used on the same axle or on plural axles can unfavorably alter the caster and camber of the wheels and the braking of the vehicle and can lead to severe tire wear. Also with the increasing use, on motor vehicles, of limited-slip differentials and front-wheel drives it is more important than ever that motor vehicle mechanics and operators have a simple device when they can use to compare the diameters of tires frequently, so that the tires may be interchanged or replaced as necessary to maintain matched or substantially matched diameter tires on each axle. If, for example, the tires on opposite ends of an axle including a limited slip differential are not of substantially equal diameter, then the differential is always slipping unnecessarily which causes excessive wear thereof.
Gages for measuring and comparing the diameters of tires are known in the prior art; U.S. Pat. Nos. 2,566,407; 2,566,435; 2,841,874 and 3,783,523 are mentioned by way of example. However, although each of the devices of this type known to me can be used to measure the outside diameter of a tire, all of them are somewhat complex and include a considerable number of parts which increases manufacturing problems and costs. They are also cumbersome, and because of this and their intricacies they are somewhat difficult and inconvenient to use